The present technology relates to a circuit board which mounts an imager, and more particularly, to a circuit board which has a compact structure without blocking a light receiving surface of the imager and is capable of efficiently regulating a temperature of the imager.
From the past, dark current noise is a target to be suppressed for an imager which detects very weak signals. The dark current noise arises because of electric charges generated by heat. Therefore, it is contemplated that the temperature of the imager is regulated constantly as one of measures to suppress the dark current noise. Moreover, in a case of evaluating characteristics of the imager, evaluation conditions need to be constant. Even in this point, it is desirable that the temperature of the imager be regulated constantly.
Thus, it is important to regulate the temperature of the imager constantly and as techniques according to the related art for regulating the temperature of the imager constantly, the following three techniques are well-known.
A first technique is a technique for constantly regulating the temperature of the imager indirectly (hereinafter, referred to as an indirect temperature regulation technique) by bringing a temperature regulation member such as a heat sink and a Peltier element into contact with a circuit board to which the imager is mounted (see, for example, Japanese Patent Application Laid-Open No. 6-233311). A second technique is a technique for constantly regulating the temperature of the imager (hereinafter, referred to as a thermostatic bath temperature regulation technique) by installing an entire circuit board to which the imager is mounted in a thermostatic bath. A third technique is a technique for constantly regulating the temperature of the imager (hereinafter, referred to as an air supply temperature regulation technique) by supplying air to the entire circuit board to which the imager is mounted.